Child Obesity

Too Many Kids Are Too Heavy, Too Young

Childhood obesity has been called “one of the most serious public health challenges of the 21st century,” and with good reason. (1)

Obesity can harm nearly every system in a child’s body—heart and lungs, muscles and bones, kidneys and digestive tract, as well as the hormones that control blood sugar and puberty—and can also take a heavy social and emotional toll. (2) What’s worse, youth who are overweight or obese have substantially higher odds of remaining overweight or obese into adulthood, (3) increasing their risk of disease and disability later in life.

Globally, an estimated 43 million preschool children (under age 5) were overweight or obese in 2010, a 60 percent increase since 1990. (4) The problem affects countries rich and poor, and by sheer numbers, places the greatest burden on the poorest: Of the world’s 43 million overweight and obese preschoolers, 35 million live in developing countries. By 2020, if the current epidemic continues unabated, 9 percent of all preschoolers will be overweight or obese—nearly 60 million children. (4)

Obesity rates are higher in adults than in children. But in relative terms, the U.S., Brazil, China, and other countries have seen the problem escalate more rapidly in children than in adults. (5)

Of course, some regions still struggle mightily with child hunger, such as Southeastern Asia and sub-Saharan Africa. (6) But globalization has made the world wealthier, and wealth and weight are linked.

As poor countries move up the income scale and switch from traditional diets to Western food ways, obesity rates rise. (7) One result of this so-called “nutrition transition” is that low- and middle-income countries often face a dual burden: the infectious diseases that accompany malnutrition, especially in childhood, and, increasingly, the debilitating chronic diseases linked to obesity and Western lifestyles.

It’s surprisingly challenging to track childhood obesity rates across the globe. Many countries do not field nationally representative surveys that measure heights and weights of school-aged children, or don’t have repeated consistent measurements over time. Dueling definitions of childhood obesity—from the U.S. Centers for Disease Control and Prevention (CDC), the World Health Organization (WHO), and the International Obesity Task Force (IOTF)—further complicate matters, making it hard to compare data between regions.

This article gives a brief overview of global obesity trends in children. A related article covers obesity trends in adults.

North America

Over the past three decades, childhood obesity rates have tripled in the U.S., and today, the country has some of the highest obesity rates in the world: one out of six children is obese, and one out of three children is overweight or obese. (8) Though the overall U.S. child obesity rate has held steady since 2008, some groups have continued to see increases, and some groups have higher rates of obesity than others:

In the 1970s, 5 percent of U.S. children ages 2 to 19 were obese, according to the CDC’s current definition; by 2008, nearly 17 percent of children were obese, a percentage that held steady through 2010. (8,9)

Obesity is more common in boys than girls (19 percent versus 15 percent). (8)

Obesity rates in boys increased significantly between 1999 and 2010, especially among non-Hispanic black boys; but obesity rates in girls of all ages and ethnic groups have stayed largely the same. (8)

Nearly 10 percent of U.S. infants had a high “weight for recumbent length”—a measure that’s similar to the body mass index but used in children from birth to age 2. (8)

From 1999 to 2010, Mexican American infants were 67 percent more likely to have a high weight for recumbent length than non-Hispanic white infants. (8)

Canada has also seen a rise in childhood obesity since the late 1970s—overall, obesity rates have more than doubled, and in some age groups, tripled. (10) But childhood obesity rates are still a good bit lower there than they are in the U.S. In 2007–2008, nearly 9 percent of Canadian youth ages 6 to 17 were obese, based on the IOTF age-specific cutoffs. (10) Child obesity is a bigger problem among Canada’s Aboriginal groups: A survey of Aboriginal groups who live outside of reservations found that in 2006, nearly 33 percent of children ages 6 to 8 were obese, as were 13 percent of children ages 9 to 14. (10)

Though data are scarce from Latin America and the Caribbean, it’s clear that childhood overweight and obesity have become sizable problems—and that overall, more children in the region are overweight than underweight.

Preschoolers

Roughly 7 percent of children under the age of 5 in Latin America and the Caribbean were estimated to be overweight or obese in 2010, according to the WHO growth standards. (4) While under-nutrition remains a concern in this age group, the region has seen substantial reductions in child underweight over the past two decades, from 7 percent in 1990 to 3 percent in 2010. (6)

School-Age Children and Adolescents

Nationally representative data are limited in these age groups, but again, the best available data suggest that obesity has become a serious problem. In Mexico, for example, a 2006 government health survey measured heights and weights of children across the country. It found that nearly 10 percent of 15-year-olds were obese and 33 percent were overweight or obese, using the adult cut points for overweight (BMI of 25 or higher) and obese (BMI of 30 or higher), cut points that likely underestimate the true rates of overweight and obesity in adolescents. (11) In Argentina, meanwhile, investigators measured heights and weights from a representative sample of 1,688 children ages 10 to 11 in Buenos Aires’ public schools. They found that 35 percent of the children were overweight or obese, using the CDC’s definition, and about 4 percent were underweight. (12) Of note, stunting and overweight coexist in many developing countries, and stunting my increase the risk of obesity later on in life.

Surprisingly, Europe has less-than-complete data on childhood obesity trends, especially from eastern countries. And until recently, data were not gathered in a consistent way across the continent, making it very hard to compare numbers from country to country. But the best available estimates find that over the past few decades, obesity rates have been rising among children in many countries. (13,14) More recently, rates seem to have hit a plateau in a few countries, among some age groups:

Preschoolers

Overweight and obesity rates at 4 years of age vary quite a bit from country to country, according to a recent systematic review of studies from the 27 countries in the European Union (EU). Spain had the highest rate—just over 32 percent—and Romania had the lowest rate, about 12 percent. (14) Keep in mind, though, that only 18 of 27 countries had data available, and often, the sample sizes were small or the data had other limitations. Five countries had repeated surveys of children ages 2 to 5, offering a glimpse of trends over the past few decades—the Czech Republic, England, France, the Netherlands, and Romania. Of those, only England showed a rise in obesity rates, from about 18 percent in 1995 to 23 percent in 2002.

School-Age Children

The World Health Organization European Childhood Obesity Surveillance Initiative recently began tracking child obesity rates across 15 countries, using the WHO child growth standards. The first analysis, based on 2007–2008 data from 13 countries (Belgium, Bulgaria, Cyprus, Czech Republic, Ireland, Italy, Latvia, Lithuania, Malta, Norway, Portugal, Slovenia, Sweden), finds that 24 percent of European children ages 6 to 9 are overweight. (15) A second wave of data collection, in 2010, has yet to be reported. Over time, this survey should offer more insights into European trends within and across countries.

Adolescents

Cyprus, Greece, Spain, and England have some of the highest obesity rates among youth ages 10 to 18, according to a recent systematic review of studies from 30 countries (the 27 EU members plus Iceland, Norway, and Switzerland). (13) But again, the data are limited and of varying quality; only 18 of 30 countries had nationally representative data from measured heights and weights. Fourteen countries had trend data available, though some were based on self-reported measures with small samples. (13) Most of these countries showed increases in obesity rates over the past few decades. France, however, showed no changes in obesity rates from 1998 to 2007 in children ages 3 to 14, a finding echoed by subsequent reports. (16–18) Sweden saw no change from 2001 to 2007 among 16-year-old youth, and a more recent review finds obesity rates have held steady in other age groups as well.(18)

Hunger, underweight, and stunting have long been the more pressing child nutrition concerns across Africa, and even today, 20 to 25 percent of preschoolers in sub-Saharan Africa are underweight. (6) Yet here, too, child obesity rates are on the rise: The percentage of preschoolers in Africa who are overweight or obese more than doubled over the past two decades, from 4 percent in 1990 to 8.5 percent in 2010. (4) A closer look at the numbers, though, shows much higher rates in Northern Africa than the rest of the continent:

Preschoolers

In Northern Africa, an estimated one in six preschool-aged children is overweight or obese—the highest rate in the world, and triple that in 1990. (4) There’s quite a bit of variability from country to country, however: About 20 percent of Egypt’s preschoolers were overweight or obese in 2008, compared with 5 percent in Sudan. (4)

In sub-Saharan Africa, meanwhile, overweight and obesity rates among preschoolers are still in the single digits—roughly 9 percent in Middle Africa, 6 percent in Western Africa, 7 percent in Eastern Africa, and 8 percent in Southern Africa. (4) But for most of the region, these rates are double or triple what they were two decades ago; only Southern Africa has seen the rate drop slightly since 1990.

Children and Adolescents

There are scant few nationally representative surveys available from older youth in the region, but available data suggest obesity is increasing in this age group, as well. In South Africa, for example, only about 1 percent of youth ages 8 to 11 were overweight or obese in 1994, based on the IOTF cut points. (19) By 2006, about 17 percent of South African girls and 11 percent of boys ages 6 to 13 were overweight or obese. (20)

Even though child hunger remains the most pressing nutritional concern for much of Asia—in South Asia, for example, one in three preschool children is underweight—the region has also seen dramatic increases in child obesity. Overall in Asia (excluding Japan), nearly 5 percent of preschoolers were estimated to be overweight or obese in 2010, a 53 percent increase in prevalence since 1990. (4) That translates into 17.7 million Asian preschoolers being overweight or obese.

There’s quite a bit of diversity from region to region, however. While South Asian countries like Bangladesh, India, and Pakistan have low obesity rates, their large populations add up to large numbers of children who are overweight or obese.

It’s important to note that in Asian adults, the health complications associated with overweight and obesity start at a lower BMI than seen in the U.S. and Europe. So many of these estimates of child obesity prevalence in Asia likely underestimate the true public health burden of obesity in Asia.

Preschoolers

In 2010, preschooler obesity rates were far higher in Western Asia (which includes the Middle East) than in Eastern, Southeastern, or South Central Asia (roughly 15, 5, 5, and 4 percent, respectively). (4) But South Central Asia had the largest number of overweight preschoolers of any region on the world—an estimated 6.6 million children. (4)

School-Age Children and Adolescents

Nationally representative data are scarce for older children in Asia, but taken together, paint a worrisome picture of obesity trends. In China, over the past 20 years, nationally representative studies of youth ages 8 to 18 have shown a dramatic rise in obesity: In 1985, only 2 percent of boys and 1 percent of girls were overweight or obese, based on Chinese-specific cut points (at age 18, a BMI of 24 for overweight and 28 for obesity). By 2005, roughly 14 percent of boys and 9 percent of girls were overweight or obese—a total of 21 million children. (21) In India, meanwhile, the largest study to date covered five urban areas and included nearly 40,000 children ages 8 to 18. It found that 14 percent were overweight or obese—a number that, if extrapolated to urban youth across India, amounts to an estimated 15 million children. (20) In Western Asia, the Arabian Gulf States have especially high rates of overweight and obesity among schoolchildren. A nationally representative Kuwaiti survey in 2006 found that about 44 percent of boys and 46 percent of girls ages 10 to 14 were overweight or obese, according to the CDC’s pre-2000 definition. (22)

Oceania

The major developed countries in Oceania—Australia and New Zealand—have childhood obesity rates in the double digits, but there’s some evidence that rates have hit a plateau over the past decade. (18,23)

In Australia, a systematic review of 41 studies from 1985 through 2008 found that obesity rates in children ages 2 to 18 rose through the mid-1990s, but have held relatively stable since then. (23) In 2008, 21 to 25 percent of Australian boys and girls were overweight or obese, and 5 to 6 percent were obese.

In New Zealand, nationally representative data show that about 28 percent of children ages 5 to 14 were overweight or obese in 2006–2007, a rate that was unchanged from 2002. (18) Overweight and obesity rates are much higher in some of New Zealand’s ethnic groups (Maori, 37 percent, and Pacific Islanders, 57 percent), but are also largely unchanged since 2002.

The Bottom Line: It’s Never Too Early to Start Preventing Obesity

Even among the youngest of children, it’s clear that obesity rates are rising across the globe. Equally clear is that it’s very, very hard for anyone who becomes overweight to lose weight, at any age. Preventing obesity in a child’s earliest years (and even before birth, by healthy habits during pregnancy) confers a lifetime of health benefits. And it’s the most promising path for turning around the global epidemic. (24)

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The aim of the Harvard School of Public Health Obesity Prevention Source Web site is to provide timely information about obesity’s global causes, consequences, prevention, and control, for the public, health and public health practitioners, business and community leaders, and policymakers. The contents of this Web site are not intended to offer personal medical advice. You should seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this Web site. The Web site’s obesity prevention policy recommendations are based primarily on a review of U.S. expert guidance, unless otherwise indicated; in other countries, different policy approaches may be needed to achieve improvements in food and physical activity environments, so that healthy choices are easy choices, for all.

Defining Childhood Obesity

The World Health Organization, (25,26) U.S. Centers for Disease Control and Prevention, (27,28) and International Obesity Task Force (29) have different definitions of overweight and obesity in children. At different ages, these criteria give somewhat different estimates of overweight and obesity prevalence. (30)